setting phase on subwoofer with a dB-meter - AVS Forum
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post #1 of 11 Old 06-16-2012, 11:45 PM - Thread Starter
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I have a dB meter and want to find the right phase setting for my subwoofer. Am I correct that I can do this by:

- Run my front speakers on +-75dB with a 80Hz test tone.
- Disable the front speakers and put the subwoofer on a volume that results in +-75dB also with 80Hz test tone.
- After this run both subwoofer and main speakers and adjust the phase rotation button of my subwoofer and find the value on my dB meter that gives me the HIGHEST result.

Thanks.

My setup:
Marantz SR5005
Teufel Theater 8 5.1 THX-UltraII
dB-meter: http://www.elektro-rama.nl/contents/nl/p1201.html
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post #2 of 11 Old 06-17-2012, 12:48 AM
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Make sure the crossovers for the speakers and sub are disabled when you run the 80hz test tone to set the level at 75db. Correct phase would be having a 75db result with both playing and the crossover engaged.


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post #3 of 11 Old 06-17-2012, 06:40 AM
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Quote:
Originally Posted by sanderdvd View Post

I have a dB meter and want to find the right phase setting for my subwoofer. Am I correct that I can do this by:
- Run my front speakers on +-75dB with a 80Hz test tone.
- Disable the front speakers and put the subwoofer on a volume that results in +-75dB also with 80Hz test tone.
- After this run both subwoofer and main speakers and adjust the phase rotation button of my subwoofer and find the value on my dB meter that gives me the HIGHEST result.
Thanks.
My setup:
Marantz SR5005
Teufel Theater 8 5.1 THX-UltraII
dB-meter: http://www.elektro-rama.nl/contents/nl/p1201.html

Instead of using the Phase setting on the sub, use the Subwoofer Distance setting in the receiver. It's a better tool for this job. Set the Phase Control on the sub to zero, and then run the 80 Hz test tone through the sub and speakers with the crossover engaged. Adjust the Subwoofer Distance for the highest reading on the SPL meter.

Craig

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post #4 of 11 Old 06-17-2012, 10:14 AM
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Your AVR has Audyssey MultEQ XT. Set the phase on your sub to 0 and run the Audyssey setup routine. It should be able to set the proper distance (phase) for your sub with greater precision than you can get with a dB meter.
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post #5 of 11 Old 07-11-2012, 11:34 PM - Thread Starter
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Quote:
Originally Posted by henrich3 View Post

Your AVR has Audyssey MultEQ XT. Set the phase on your sub to 0 and run the Audyssey setup routine. It should be able to set the proper distance (phase) for your sub with greater precision than you can get with a dB meter.
You sure about this? I thought that Audessey can never get that precise with setting a phase for the subwoofer/main speaker combination.
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post #6 of 11 Old 07-11-2012, 11:34 PM - Thread Starter
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Quote:
Originally Posted by craig john View Post

Instead of using the Phase setting on the sub, use the Subwoofer Distance setting in the receiver. It's a better tool for this job. Set the Phase Control on the sub to zero, and then run the 80 Hz test tone through the sub and speakers with the crossover engaged. Adjust the Subwoofer Distance for the highest reading on the SPL meter.
Craig
thxz for this tip
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post #7 of 11 Old 07-12-2012, 06:08 AM
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Quote:
Originally Posted by sanderdvd View Post

Quote:
Originally Posted by henrich3 View Post

Your AVR has Audyssey MultEQ XT. Set the phase on your sub to 0 and run the Audyssey setup routine. It should be able to set the proper distance (phase) for your sub with greater precision than you can get with a dB meter.
You sure about this? I thought that Audessey can never get that precise with setting a phase for the subwoofer/main speaker combination.

My impression after reading some of the relevant posts on the Audyssey website is that subwoofer phase knobs do not shift phase consistantly across the entire range of frequencies that they cover. For example, the delay at 80 Hz may be significantly different than the delay at 40 Hz. Also, when you do a manual phase adjustment you've just adjusted it at a single location and frequency. If you run the Audyssey setup routine with it's mic in 6 different locations, Audyssey will calculate the ideal compromise delay (distance) based on the combined measurements.

You should be able to test to see if theory & reality line up. Put the Audyssey mic on a tripod in the primary listening position. Run through the Audyssey setup leaving the mic in that same position for each measurement. Check out the sub's distance in your receiver. Now place your dB meter in the tripod in the same location. See if you can get a significantly better gain at the crossover frequency with a manual adjustment. If not, then you've confirmed that Audyssey works as advertised. Rerun the Audyssey setup with the mic in different locations to then get a better correction. Go back after the Audyssey run to ensure your preferred settings are in the receiver (speakers to "small", crossovers at 80 Hz, etc.).
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post #8 of 11 Old 07-12-2012, 10:55 AM
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Quote:
Originally Posted by sanderdvd View Post

You sure about this? I thought that Audessey can never get that precise with setting a phase for the subwoofer/main speaker combination.
If you are just using a single sub, Audyssey generally gets it very close. You may be able to optimize it a bit more with the subwoofer Distance setting, (don't use the subwoofer phase control for the very reason henrick3 describes:

Quote:
Originally Posted by henrich3 View Post

My impression after reading some of the relevant posts on the Audyssey website is that subwoofer phase knobs do not shift phase consistantly across the entire range of frequencies that they cover. For example, the delay at 80 Hz may be significantly different than the delay at 40 Hz. Also, when you do a manual phase adjustment you've just adjusted it at a single location and frequency.

Quote:
Originally Posted by henrich3 View Post

If you run the Audyssey setup routine with it's mic in 6 different locations, Audyssey will calculate the ideal compromise delay (distance) based on the combined measurements.
Yes, Audyssey will do this. ^ However, Audyssey never goes back and verifies that the Distance setting it chooses is optimal. I am often able to optimize the subwoofer Distance setting and get a few extra dB of output at the crossover frequency.
Quote:
You should be able to test to see if theory & reality line up. Put the Audyssey mic on a tripod in the primary listening position. Run through the Audyssey setup leaving the mic in that same position for each measurement. Check out the sub's distance in your receiver. Now place your dB meter in the tripod in the same location. See if you can get a significantly better gain at the crossover frequency with a manual adjustment. If not, then you've confirmed that Audyssey works as advertised. Rerun the Audyssey setup with the mic in different locations to then get a better correction. Go back after the Audyssey run to ensure your preferred settings are in the receiver (speakers to "small", crossovers at 80 Hz, etc.).
That's pretty much what I do, except I use XTZ sweep tones. I am usually able to tweak a few dB around the crossover out of most of the systems I've set up, especially the multi-sub systems.

Craig

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post #9 of 11 Old 07-14-2012, 07:59 AM
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Quote:
Originally Posted by craig john View Post

If you are just using a single sub, Audyssey generally gets it very close. You may be able to optimize it a bit more with the subwoofer Distance setting, (don't use the subwoofer phase control for the very reason henrick3 describes:
That's pretty much what I do, except I use XTZ sweep tones. I am usually able to tweak a few dB around the crossover out of most of the systems I've set up, especially the multi-sub systems.
Craig

Craig, will you lay out the multi sub process you are using por favor?
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post #10 of 11 Old 07-14-2012, 09:05 AM
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Originally Posted by dstew100 View Post

Craig, will you lay out the multi sub process you are using por favor?
I've done this numerous times. Here is probably the most elaborate post I've made: http://www.avsforum.com/t/759877/seaton-sound-submersive1/4500#post_19446901 The discussion about setting the Distances follows a few posts below: http://www.avsforum.com/t/759877/seaton-sound-submersive1/4500#post_19450333

There is also a thread on gain-matching vs. level-matching, which I think is equally important for multi-sub systems: http://www.avsforum.com/t/1282064/two-subs-gain-matching-vs-level-matching

Craig

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post #11 of 11 Old 07-15-2012, 04:43 PM
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Quote:
Originally Posted by craig john View Post

I've done this numerous times. Here is probably the most elaborate post I've made: http://www.avsforum.com/t/759877/seaton-sound-submersive1/4500#post_19446901 The discussion about setting the Distances follows a few posts below: http://www.avsforum.com/t/759877/seaton-sound-submersive1/4500#post_19450333
There is also a thread on gain-matching vs. level-matching, which I think is equally important for multi-sub systems: http://www.avsforum.com/t/1282064/two-subs-gain-matching-vs-level-matching
Craig

thanx
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